1. Field of the Invention
The invention relates to a method and apparatus for the segregation and separate recovery of low density solids and high density solids from mixtures of the same. More specifically, the invention involves segregation and separate recovery of substantially non-buoyant low density solids in a liquid medium.
2. Description of the Prior Art
Liquids and especially water have long been used in segregating light and heavy fractions of mixtures. Where one particular faction of the mixture has a density which is about the same as that of water, workers in the art have typically increased the density of water by adding salt or brine to the water. The brine solution is then used to recover the light or low density solids by floatation. Such brine floatation techniques have long been used in the mollusk industry for the recovery of clam meats and oyster meats from mixtures of free meat and shell. The mollusk meats have a bulk density which is about that of water.
Brine solutions often adversely affect the quality of food products and there have been continuous efforts in the art to discover and design other techniques for segregating and recovering solids such as clam and oyster meats which have bulk densities about the same as water.
The so-called "oyster blower" which consists of an open-top tank containing water and having a perferated spreader pipe in its bottom by which air is continuously bubbled through the water has been used in the oyster industry and in the clam industry to separate pieces of shell and sand from oyster and clam meats. Typical uses of the "oyster blower" apparatus involve introducing whole oysters or ground or whole clams into the top of the tank at one end thereof and floating the meats to the other end of the tank during a time of from about one-half to several minutes. Such techniques are discussed in U.S. Pat. No. 2,808,615 to H. F. Snow.
U.S. Pat. No. 3,722,035 Hanks discloses a method and apparatus which is said to remove attached meat from the shells of bivalved mollusk. Whole clams are conditioned to partially open their shells and the clams with meat lightly adhering to the shells are introduced into a tank of water containing upwardly rising air bubbles. The conditioned mollusks fall through the water through the zone of rising air bubbles which is said to cause both the separation of meat from the shell and floatation of the clam meat to the top of the tank where it is removed. Systems such as the oyster blower system, the Hanks system and various other attempted methods which rely on air bubbles for floating and segregating mollusk meat still have need for considerable improvement.
Thus, when attempts are made to operate such systems rapidly, the quality of the segregation of the light solids and the heavy solids decreases resulting either in loss of recoverable meat or an ineffective segregation, i.e. the inclusion of significant amounts of contaminants such as shells along with the meat fraction. Thus, there is a continuing need for improvement in the art.